Microsoft has released SQL Server 2019 CU5:
This article describes Cumulative Update package 5 (CU5) for SQL Server 2019. This update contains fixes that were released after the initial release of SQL Server 2019 and updates the SQL Server and Analysis services components to the following builds.
I see a half-dozen or so PolyBase-related fixes, though I was hoping to read that they’ve fixed the issue around creating and using external objects when you are connected to SQL Server via Windows authentication. I’ll have to test that out to see if it was fixed—that was broken in CU3 and remained so in CU4.